Problem: Express your answer in scientific notation. $2.3 \cdot 10^8 + 4.7 \cdot 10^7 = $
Explanation: $\phantom{=} {2.3 \cdot 10^8} + 4.7 \cdot 10^7$ $={23 \cdot 10^{7}} + 4.7\cdot10^{7} $ $= (23+4.7)\cdot10^{7}$ $=27.7\cdot10^{7}$ $= 2.77\cdot10^{8}$